[DRILL-536] HashAggregate encounters NPE when no aggregate functions are present

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.4.0
• Assignee: Aman Sinha
• Reporter: Aman Sinha
• Created: 16/Apr/14 22:53
• Updated: 31/Jul/14 06:33
• Resolved: 20/Apr/14 04:08

Description

For a plan that contains only group-by keys and no aggregate functions, we encounter a NPE, which is coming during code generation. See below. The physical plan to reproduce is also given below.

{
head : {
version : 1,
generator :

{ type : "optiq", info : "na" }

,
type : "APACHE_DRILL_PHYSICAL"
},
graph : [ {
"pop" : "parquet-scan",
"@id" : 1,
"entries" : [

{ "path" : "tpch/nation.parquet" }

],
"storage" :

{ "type" : "file", "connection" : "classpath:///" }

,
"format" :

{ "type" : "parquet" }

}, {
pop : "project",
@id : 2,
exprs : [

{ ref : "output.$f0", expr : "N_REGIONKEY" }

,

{ ref : "output.$f1", expr : "N_NATIONKEY" }

,

{ ref : "output.$f2", expr : "N_NAME" }

],
child : 1
}, {
pop : "hash-aggregate",
@id : 3,
child : 2,
keys : [

{ ref : "$f0", expr : "$f0" }

,

{ ref : "$f1", expr : "$f1" }

,

{ ref : "$f2", expr : "$f2 " }

]
},

{ pop : "screen", @id : 4, child : 3 }

]
}

java.lang.NullPointerException
org.apache.drill.exec.physical.impl.aggregate.HashAggBatch.createAggregatorInternal(HashAggBatch.java:184) ~[classes/:na]
org.apache.drill.exec.physical.impl.aggregate.HashAggBatch.createAggregator(HashAggBatch.java:165) ~[classes/:na]
org.apache.drill.exec.physical.impl.aggregate.HashAggBatch.next(HashAggBatch.java:112) ~[classes/:na]
org.apache.drill.exec.physical.impl.validate.IteratorValidatorBatchIterator.next(IteratorValidatorBatchIterator.java:107) ~[classes/:na]
org.apache.drill.exec.physical.impl.ScreenCreator$ScreenRoot.next(ScreenCreator.java:85) ~[classes/:na]
org.apache.drill.exec.work.fragment.FragmentExecutor.run(FragmentExecutor.java:83) ~[classes/:na]